Establishing HIV transmission pathways in Bhutan: a modelling study.

Background: There are limited and conflicting data regarding HIV transmission and behavioural risk factors, particularly among groups with increased risk of exposure to HIV in Bhutan. This study aims to explore comprehensive pathways to HIV infections among key populations in Bhutan. Methods: Demographic, epidemiological, and behavioural data were collated to inform an Optima HIV model for Bhutan. The model was calibrated for a period 1990 and 2021 to align with emerging national research into risk attribution of HIV infections and behavioural dynamics of key populations. This was supplemented by qualitative feedback from stakeholder consultations throughout January-June 2022, while maintaining the consistency of the country-accepted output from the 2022 Estimation and Projection Package (EPP-Spectrum model) across all years. Findings: In 2021, sex work was directly associated with 54% of new HIV infections. In total, 86% of new HIV infections were estimated to be among key and vulnerable populations, their direct partners, and their children. HIV prevalence remained low, ranging from 0.7% to 3.1% among key populations. Due to the relatively short duration of risk activity (average of three years among female sex workers [FSW]), only an estimated 9.7% of undiagnosed people living with HIV could be reached through interventions focused on key populations. Interpretation: Greater efforts in developing strategies that can prevent new HIV infections among individuals currently at risk-and identifying undiagnosed HIV infections among those with historic risk who are not currently accessing HIV services-could help achieve the elimination of HIV transmission in Bhutan. Funding: This analysis was funded through The Sustainability of HIV Services for Key Populations in Southeast Asia (SKPA-1) project, funded by the Global Fund to Fight AIDS, Tuberculosis and Malaria under agreement QMZ-H-AFAO, with Health Equity Matters as Principal Recipient. Save the Children is the sub-recipient of SKPA in Bhutan.